1. Field of the Invention
The present invention relates to a chain guide having a guide shoe that slidably guides a running chain, and a base member that supports the guide shoe along a guide longitudinal direction.
2. Description of the Related Art
A chain guide has hitherto been known, which is incorporated in a timing system in the engine room of a car for slidably guiding a chain running between sprockets to keep an appropriate chain tension (see, for example, Japanese Patent Application Laid-open No. 2006-242357).
This chain guide described in Japanese Patent-Application Laid-open No. 2006-242357 is formed by a guide shoe that slidably guides the running chain,, and a base member that supports the guide shoe, and configured such that the guide shoe is removably attached to the base member by means of a plurality of hooks formed to the guide shoe and engaged with engagement portions of the base member.
In such a chain guide, it is also known to restrict sideway displacement of the guide shoe relative to the base member to achieve stable movement of the chain in sliding contact with the guide shoe, and also to provide side wall ribs on the upper face of the base member such as to stand on the left and right side edges in the guide width direction, for the purpose of enhancing the strength of the base member by utilising available space on the guide shoe side (see, for example, Japanese Patent Application Laid-open No. 2005-036275).
However, with side wall ribs formed on the left and right side edges of the base member as in the chain guide described in Japanese Patent Application Laid-open No. 2009-036275, part of the base member where the side wall ribs are formed cannot be utilized as the location for the hooks of the guide shoe to be engaged. Therefore, the location available for engagement of the hooks of the guide shoe is limited to the upstream side and downstream side relative to the side wall ribs of the base member.
In the chain guide described in Japanese Patent Application Laid-open No. 2009-036275, an upstream hook (chain entrance-side engaging portion) formed to the guide shoe is engaged with an upstream engagement portion (chain entrance-side engagement portion) formed at an upstream end of the base member, and a downstream hook (chain exit-side engaging portion) formed on a downstream side of the guide shoe is engaged with a downstream engagement portion (chain exit-side engagement portion) formed to the base member on a downstream side of the side wall ribs, so as to prevent the guide shoe from lifting up from the base member on the upstream side and downstream side of the side wall ribs. Movement of the guide shoe relative to the base member in a guide longitudinal direction is restricted such that movement of the guide shoe toward a downstream side relative to the base member is restricted by the engagement between the upstream hook and the upstream engagement portion, while movement of the guide shoe toward an upstream side relative to the base member is restricted by the engagement between an engagement recess formed in an upper face of the base member and a shoe-backside protrusion protruded on the underside of the guide shoe.
According to this chain guide described in Japanese Patent Application Laid-open No. 2009-036275, to attach the guide shoe to the base member, first, the downstream hook is hooked to the downstream engagement portion, and then the upstream hook is hooked to the upstream engagement portion, after which the guide shoe is moved toward the downstream side relative to the base member in order to insert the shoe-backside protrusion into the engagement recess.